Cardiovascular adjustments to cold pressor test in postmenopausal women and the impact of α1-adrenergic blockade.

PURPOSE

We investigate the impact of menopause on cardiovascular adjustments to the cold pressor test (CPT) and the role of the α1-adrenergic receptor.

METHODS

Ten young women (YW) and nine postmenopausal women (MW) underwent 1 min of CPT in control and α1-blockade conditions (0.03 mg‧kg of oral prazosin).

RESULTS

CPT increased heart rate (HR) (YW: ∆20 ± 3 bpm; MW: ∆13 ± 2 bpm) and stroke volume (SV; YW: ∆15 ± 8 ml; MW: ∆9 ± 6 ml; p = 0.01 for time) and evoked a greater increase in cardiac output (CO) in YW (YW: ∆2.1 ± 0.2 l‧m; MW: ∆1.3 ± 0.5 l‧m; p = 0.01). α1-Blockade increased baseline HR and did not change HR, SV, and CO responses to CPT. MW presented an exaggerated systolic blood pressure (BP) response (YW: ∆38 ± 9 mmHg; MW: ∆56 ± 24 mmHg; p = 0.03). The α1-blockade did not change baseline BP while blunting its response. Total vascular resistance (TVR) was similar between groups at baseline and increased during CPT only in MW (YW: ∆2.3 ± 1.4 mmHg‧L‧min; MW:∆6.8 ± 5.9 mmHg‧L‧min). Under α1-blockade, the TVR increase during CPT was attenuated in MW and abolished in YW (YW: ∆0.3 ± 1.2 mmHg‧L‧min and MW: ∆3.0 ± 2.0 mmHg‧L‧min). CPT did not change femoral vascular conductance (FVC) in either group before the blockade (YW: ∆-0.3 ± 4.0 ml‧min‧mmHg; MW: ∆-0.2 ± 0.8 ml‧min‧mmHg); however, FVC tended to increase in young women (YW: ∆1.3 ± 1.0 ml‧min‧mmHg; MW: ∆0.1 ± 1.5 ml‧min‧mmHg; p = 0.06) after the α1-blockade.

CONCLUSION

In postmenopausal women, the cardiac ability to adjust to CPT is blunted and α1-adrenergic receptor stimulation is important for the increase in stroke volume. In addition, the peripheral effect of α1-adrenergic receptor stimulation seems to be increased in postmenopausal women.